Cannot upload sketch to teensy 4.0

[Thundercat]

Hi, I've been using the platform for a few years, and have used many many dozen Teensy 4.0s.

I recently flashed a new Teensy 4.0, no issue, and tonight I tried to update it, but the Teensy loader program fails. It just says to press the button on the Teensy, and when I do, it fails again and says to press the button on the Teensy.

I've tried replacing the cable, rebooting, using a powered USB hub, going directly to the computer, but nothing seems to break out of this infernal loop.

I'm attaching the log file here in case any brilliant minds can shed light on what may be going on.

Thanks for any insights,

Mike

PS I'm using a Mac, latest OS Sonoma 14.3.1

 

[Thundercat]

Does anyone have any thoughts? This is a brand new Teensy. They're usually pretty bulletproof.

I can add that this is a lockable Teensy 4.0, and it's locked, and I've been using lockable Teensys like this for a long time.

It simply fails to upload the sketch.

Thanks for any thoughts.

Mike

 

[PaulStoffregen]

I'm attaching the log file here in case any brilliant minds can shed light on what may be going on.

I'm sad to say, this is the one place where we really can't get much info. The log file show the USB device is appearing and Teensy Loader is sending the loader utility. The USB disconnects, which probably means the loader utility started running, but even that is basically guesswork. The NXP security model just doesn't let us see anything, until the loader utility is successful and we're into normal Teensy bootloader mode.

It's just a shot in the dark, but maybe try looking for damage or stray solder in the area between U1 and U2. As with Teensy not locked in secure mode, anything that disrupts the connection between those 2 chips generally prevents going into bootloader mode.

 

[Thundercat]

Thank you Paul. I will examine the board.

However, I had already successfully flashed it several times. Seems more than odd that stray solder would become a problem 2-3 weeks later…

In any case, I appreciate your expertise.

If I find anything noteworthy I will reply here again.

Thank you so much.

Mike

 

[Thundercat]

Just an update. I examined the board carefully, and no visible damage anywhere. I did what I never do - flooded the whole thing with 99% isopropyl alcohol and brushed it vigorously with a brush - to remove all traces of flux from the board. I use a "no clean" flux that hasn't caused any issues, and I normally leave the flux on the pins as I don't want to get alcohol inside the program button.

Anyway, I was able to flash it once, but unfortunately had forgotten to switch the LCD setup to the right one, so it flashed but then refused to display anything. I corrected the software issue and tried to reflash, but alas, back to the same old story - not able to flash.

So again, I flooded the teensy with alcohol, used a brush, it's sparkling clean now (and perhaps not good for the program button!). But I was able to finally flash it with an update and the unit is working.

I have dismal hopes for future updates, but in case this helps anyone, even a no-clean flux can apparently interfere with the delicate circuitry on these lil' guys.

I feel like these Teensys have some sort of innate gift of wanting to survive. It's a testament to Paul's genius that they are so incredibly reliable over such a wide range of circumstances, and abuses. Although I didn't abuse this one!

Many thanks Paul for the (as-usual) stellar support!